Many applications currently exist for sharing screen data among a number of computer users. When a presenter changes the screen data currently being shared, the changes may then be transmitted to the other users such that their screen data is also updated. For example, applications exist which allow a slide presentation displayed on a given computer to be transmitted across a network such that the presentation can be viewed by a number of viewers. When the presenter changes to a new slide, the change may then be transmitted to all the viewers such that their screens may be updated.
However, in many networks transmission of data may involve unknown latencies or loss rates. Thus a given presenter may not know whether a given change to the shared screen data has been received by all the viewers of a presentation. The presenter may wish to wait for a given number of users, or to tailor his or her remarks appropriately for the visual data actually received by the viewers. Thus there exists a need for displaying to a presenter information corresponding to the changes in screen data that have been received by a given viewer or viewers.